Heat transfer apparatus



Oct. 18, 1932. G. c. DERRY I HEAT TRANSFER APPARATUS Original Filed Aug; 10, 1928 jvenim" Win an M W ZiSheets-Sheet 2 JZZ m G. c. DERRY HEAT TRANSFER APPARATUS Original Filed Aug.. 10, 1928 Oct. 18,1932.

WdneJI Patented a. 1a, 1932 NETEE) STATES PATENT oF icE GARDNER C. DERBY, OF SHARON, MASSACHUSETTS, ASSIGNOR TO B. RSTURTEVANT COMPANY, OF HYDE PARK, MASSACHUSETTS, A CQRPGRATIQN OF MASSACHUSETTS j HEAT TRANSFER APPARATUS Original application filed August 10, 1928,Seria1 No. 298,804. Divided and this applicationfiled."v

- February 15, 1930.

for combustion by means of hot waste gases from a furnace.

As boiler pressures and furnace temperatures in steam plants have increased from time totime, the temperatures of the waste gases have correspondingly increased. As a result, there has been an increased demand in apparatus for abstracting and converting into useful work such waste heat or a substantial part of it. One type of apparatus has utilized such waste heat for the purpose of preheating the air supply for the combustion of the fuel in the furnace, and the principal object of the present invention is to provide a heat transfer apparatus especially designed and adapted for such use.

In this type of apparatus it is desirable to avoid, so far as possible, all leakage between the air and gas conduits or chambers, one way or the other accordingto the relative pressuresf. There the pressure of the gas exceeds that of the air, any leakage will result in the admission of gases from the furnace into the air for combustion, with the resulting dilution of the latter and interference with the proper burning of the fuel. Onthe other hand, in the more common ar-.

rangement where the pressure of the air exceeds that of the gas, any leakage of air into the gas stream will result in a waste of power by the forced draft, air-handling fan, and a loss of stack draft through cooling of the gases by the lower temperature air.

One of the bbjects of the present invention is to provide a construction which, while facilitating the heating of the air by waste gases, and quick and easy removal and replacement of the parts subject to deterioration, will reduceto a 'minimum'the liability of leakage in the apparatus.

r I Another object of the present invention is so to construct the air passages as to direct and control the flow of air through the apparatus so that a minimum expenditure of energy will be required for moving such air. i

Serial No. 428,620.

- Still another object of the invention is to provide a construction in which. the parts of the heater may be produced at a minim-um costof manufacture and assembling, with efficiency in operation.

l/Vith the'seand-other objects in view, as

will be apparent to those skilled in the art from the following description, the present invention consists in the heat exchange apparatus hereinafter described and more particularly defined in the claims.

In the accompanying drawings which illustrate What is now considered the preferred form of the present invention, as applied to an air heater for power plants, Fig.- l is a side elevation of the heater showing the air and gas connections Fig. 2 is a side elevation and Fig. 3 is a front elevation of one of the air chambers detached; Fig.4: is a vertical sectionion line 4-4 of Fig. 2 looking toward the right, on an enlarged scale; Fig. 5 is a vertical sectional view on line 5-5 of Fig. 3 looking toward the right, on an enlarged scale, showing approximately the upper half of the chamber; Fig. 6 is a horizontal section on line 6-6 of Fig. 2; Figs. 7 and 8 are perspective views on a greatly enlarged scale, of certain details of construction; Fig. 9 is an enlarged perspective view of another detail of construction, namely, the channel members which are welded to the chambers at the inlet and outlet openings; Fig. 10 is a horizontal section on line 101O of Fig. 5 of the front portion of two adjacent air chambers in position in the heater; Fig. 11 is a similar view on line 11'1'1 of Fig. 5 and Fig. 12 is a detail, in vertical section, of the top front corner of the heater showing the chamber in position inthe casing. I

The heater illustrated in the accompanying drawings comprises briefly a shell or casing through which the hot waste gases pass from the bottom to thetop through suitable inlet and outlet flues. Within the casing are located a'plurality of thin air chambers or sections, closed on all sides to the gas and spacedslight distances apart from one another and from the casing to afford a large heat absorbing surface; a Each chamber. is provided at one end or edge with atop airinlet and a bottom air outlet registering respectively with the air inlet and air outlet openings or flues in the front wall of the casing. The air is forced or drawn through the air chambers by means of a fan or'other suitable draft producing means, absorbing heat from the gases through the chamber or section Walls.

Referring to Figs. 1 and 12 of the draw spectively, through which the air for com bustion is conducted to the air heater and thence to the furnace. Tt willbenoted that the air inlet and outlet are identical in size and symmetrically disposed in the front wall of of the casing.

.Within the casing are located the thin or narrow air chambers or sect ons 19. These sections comprise flat side walls 21 and 22 (see 0 Fig. 4) spaced a short distance from one another, one of the walls being bent or offset at its top, bottom and rear margins 23, and welded to the other wall as shown at 24 (see Fig. 6). By making one of these walls flat throughout its extent and giving the proper bend or ofiset to the margin of the other wall, a minimum of handling and work is required with corresponding minimum cost of manu facture.

In order to space the walls properly from one another, angle iron separators 26 (see Fig. 6) are spot welded to the walls. The middle portion of the front edge of each air chamber or section is similarly closed by bending the margin of one wall and welding it to the other one as shown at 28 (Fig. 2).

The air inlet and air outlet openings at the top and bottom of the front edge or end of the air chambers, which are of the same size and symmetricallypositioned, are formed as follows: The side walls at these-portions are cut to extend slightly beyond the intermediate portion and both are extended parallel to one another without bending, as shown at 30 in Fig. 10. At the extremity of each air opening are welded fillingpieces which not only close the ends of these openin gs but provide a support or base for the studs by means of which the air chambers or sections are secured to the front wall of the casing. Thus, at the upper end of the inlet opening is located the block (see Fig. 7) the end of which is bevelled as at 36 to fit the bevelled or bent over margin of the. side wall at this point. This block is provided with a threaded openthe stud 41 (see Fig.

ing 37 in which is secured a stud 38 (see Fig. 5). A similar filling piece is welded in the bottom end of the outlet opening of the chamber.

The filling piece for the bottom of the inlet opening and the top of the outlet opening is shown in Fig. 8 at 39, and is provided with asimilar stud-receiving opening 40 for Both of the filling blocks have bevelled front edges 42 to provide a groove or space for the welding material.

Secured to each chamber at the inlet opening and also at the outlet opening is a channel piece or member 44, shown (in part) in enlarged perspective in Fig. 9. This member is formed with a long narrow slot 46 extending throughout nearly the length of the member but leaving at each end a solid portion 48 provided with an opening 50 to receive the securing studs 38 and 41. The free marginal portions of each side wall of certain of the channel members are bent over as shown at 52 in Fig. 9, to form beads or grooves. The other channel members are provided with straight marginal portions, as shown at 54 in Figs. 10 and 11.

The channel members are secured at the inlet and outlet openings, the front margins of the walls at each side of the openings passing through and fitting closely within the r slot or opening 46 in the channelmember as shown in Fig. 11, the parts being welded as indicated at 56.

When the chambers are assembled those having channels with hooked or beaded margins are alternated with chambers in which such margins are, straight, as shown in Fig. 11. Thus the side walls of adjacent channel members have their faces in contact with one another, and in addition, the rear edge or mar in of one is received in the bead or groove of the other, thereby preventing leakage between the chambers. i i

As an additional precaution, cement may be applied to the bead or groove to seal the joint between the parts, as indicated at 60.

The chambers are secured to the casing at their front edges by meansof the studs 38 and 41 which pass through horizontal slots in the front wall of the casing immediately above and below the inlet d outlet openings. Nuts 66 on the studs draw the sections tight against the front wall of the casing with the solid end portion 48 of the channel member 44 making a tight joint between the Chit; bers and the casing.

The sections are spaced apart and held from expansion at their middle portion by means of the vertical angle strips 68 welded to the outside of the chamber and positioned to contact with the side wall of the adjacent chamber. V

The chambers are forced into close lateral ement at their front edges in any suitable manner, as by jack-screws, the nuts 66 on the front of the sections. The sections them in position while the next chamber'is inserted and forced into place.

'In order to avoid crushing of the chambers when this lateral pressure is applied at their front edges adjacent the inlet and outlet openings, the pressure blocks 69 have been welded such openings.

7 To insure the effective utilization of all 7 portions of the air chamber or section and prevent eddies and dead spots,a seriesof bafiies have been provided inthe interior of the chamber adjacent the inlet and outlet thereof. These baflies are'formed of sheet metal bent in the arc of a circle and welded to one side of the chamber and are so located that they turn the incoming air from a horizontal to a vertical direction andthe outgoing air from a vertical to a horizontal direction, while maintaining a substantially even distribution of flowthrough both the inlet and outlet and the body of the air chamber.

In operation with the waste gases from the furnace passing upwardly through the casing, the air for combustion will enter through the inlet conduit 16 and after passing through the air chambers or sections'will be discharged through the outlet conduit 17. Owing to the thinness of the air chambers or sections the streams or currents of air pass.- ing therethrough will be heated quickly to a high temperature. Preferably the counter flow principle will be employed, as above described, so as to maintain the maximum temperature difl'erence between the gases and the air throughout the passage ofthe latter through the air heater.

The external surface of the air chamber being substantially straight and smooth, offers a minimum of resistance to the passage of the gases and at the same time, owing to the large surface area exposed to their action, quickly give up their heat to the walls of the chamber and thence to the air within.

If'the chambers become corroded on their external surfaces adjacent the upper or cold end of the heater, it will'not be necessary to discard such chambers but merely toreverse them upside down, making what was the top or cold end the bottom or hot end, where little or no further corrosion would occur, and bringing fresh uncorroded portions to the top.

- Such reversal is easily effected by removing the panels 72 at the back of the casing, and removing the nuts 66 on the studs 38 and 41 may then be separated laterally'and one or more withdrawn from the back, and since they are alike at the top and bottom, both as to location and size of air opening and position of the studs, theymay be re-inserted in inverted position and then clamped'together andsecured as before.

' lVhile thepresent invention has been described as embodied in an apparatus par ticularly designed and adapted for use as "an air heater, it is to be understood that the invention is not necessarily limited thereto but may be embodied in other forms and constructions and used for otherpurposes.

This application is a divisional application of my pending application Serial No. 298,804, filed August 10, 1928.

Having thus described the invention, what is claimed is:

' 1. A heat transfer apparatus having, in.

combination, a casing having'provision for conducting hot gases thereto and therefrom, inlet and outlet openings in .the casing'for the gases to-be heated, a series of chambers in the casing spaced apart from one another and having inlet and outlet openings adapted to register with the inlet and outlet openings in the casing, and'being provided with flanges adjacent their inlet and outlet openings,- certain of the flanges having a groove, the flange of one chamber engaging the groove-on the flange on the'adj acent chamber to closethe space between said chambers. I

2'. A heat transfer apparatus having, in combination, a casing having provision for conducting hot gases thereto and therefrom,

inlet and outlet openings inthe casing for the gases to be heated, a series of chambers in the casing spaced apart from one another and having inlet and outlet openings adapted to register with the inlet and outlet openings in the casing, and being provided with flanges adj acent their inlet and outlet openings, certain ofthejflanges having agroove, the flange .on one-chamber having surface engagement with the flange of the adj acentchamber and the edge of one flange fitting into the groove on the other flange to close the space between the. chambers. 5

3. A heat transfer apparatus having, in combination, a casing having provision for conducting hot gases thereto and therefrom,

inlet and outletopenings in the casing for the gases to be heated, a series of chambers in the casing spaced apart from one another and having'inlet and outlet openings adapted to register with the inlet and outlet openings in; the casing, and being provided with flanges ad acent their inlet and outlet openings, certain of the flanges having their margins turned back to form grooves, the

edge of the flange of one section entering the groove in the flange of the adjacent section, the groove being adapted to receive cement 'to seal the joint between the flanges and close the space between the chambers.

4. A heat transfer apparatus having, in combination, a casing for hot gases, inlet and outlet openings in the casing, a series of thin, hollow air chambers mounted in the casing, said chambers comprising flat parallel walls connected at their margins discontinuously to form air inlet and air outlet openings, a filler piece secured within each chamber between the side walls thereof each end of said openings and having provision for attachment to the casing, and members secured to the outside of the chambers adjacent the openings for closing the spaces between the chambers.

5. A chamber for heat transfer apparatus comprising a pair of substantially rectangular flat parallel side walls welded to each other at their margins to form a thin, hollow air chamber having air inlet and air outlet ports at one edge, and a series of short curved bailles for changing the direction of flow of air through the chamber, the series being obliquely disposed to the direction of flow of air.

6. A'chamber for heat transfer apparatus comprising a pair of substantially rectangular fiat parallel side walls with inletand 0utlet openings at one edge, and two disconnected series of short curved battles obliquely disposed, one opposite the inlet opening and the other opposite the outlet opening for changing the direction of flow of the air through the chamber.

7 A chamber for heat transfer apparatus comprising a pair of flat parallel side walls, one of said walls having flat marginal portions and the other having its marginal portions offset and welded to the other wall to form a thin, hollow air chamber having inlet and outlet openings at one edge, trapezoidal shaped filling pieces secured between the walls at the outer ends of the openings, and rectangular filling pieces secured between the walls at the inner ends of said openings.

8. A chamber for heat transfer apparatus comprising a pair of imperforate flat side walls united discontinuously at their edges to form a thin hollow air chamber with an air opening at the edge, and having a pressure block secured in said opening.

9. A chamber for heat transfer apparatus comprising a pair of fiat parallel side walls vith an opening at one edge and an apertured flanged member secured to said edge with its aperture in alignment with said opening, one of the flanges on said member being provided with a groove adapted to receive the flange cf the member of an adjacent chamber.

10. A chamber for heat transfer apparatus comprising a pair of flat parallel side walls chamber at each end of the opening, and an apertured flanged member having its aperture in alignment with said opening and overlying at each end the filler pieces.

11. A chamber for heat transfer apparatus comprising a pair of substantially rectangular flat parallel side walls with inlet and out let openings at one edge, and a series of spaced short curved baffles for changing the direction of flow of air through the chamber and for distributing the air evenly overthe surface of the chamber, the air being free and unrestrained adjacent the baflles.

12. A chamber for heat transfer apparatus comprising a pair of substantially rectangular flat parallel side Walls with inlet and outlet openings at theedge, and a series of uniformly spaced short curved baffles for changing the direction of flow of the air through the chamber. 7

In testimony whereof I have signed my name to this specification. i

v GARDNER C. DER-RY, 

